TY - SCIENTIA GEOGRAPHICA SINICA A1 - Liu Jian, Yang Qingshan, Zhang Yu, Liu Jie, Jiang Xiaojun T1 - Spatial Patterns Evolution and Classification of Population Aging in the Three Provinces of Northeast China Based on the County Scale Y1 - 2020-12-07 00:00:00.0 JF - SCIENTIA GEOGRAPHICA SINICA JO - SCIENTIA GEOGRAPHICA SINICA SP - 918 EP - 927 VL - 40 IS - 6 UR - {http://geoscien.neigae.ac.cn/EN/10.13249/j.cnki.sgs.2020.06.007} N1 - 10.13249/j.cnki.sgs.2020.06.007 ER -